I have wanted to do it for years but all the locations that are listed for my aria haven't been updated in 5 years so I don't even know if we went looking for one if we would find anything to know that we found the site.
We do it, but mostly on hikes. I try hard to plan ahead of time so we have something to put in the container otherwise I'm searching for something like a penny, hair thing, pencil, or whatever my kids happened to have in their pockets at the time.
It's fun, especially if it's just a side thing you're doing when you're out to do something else, like when you're walking around the lake, hiking, or just buying time before the thing you came to do.
WE DID! It was GREAT and we got to have some great experiences along the way. I'd recommend getting a trackable Geocoin and watch it travel too. Your kids can look up on the map where the coin is going. Ours traveled all over the world.
Also, learning to use a GPS for navigating to caches, learning about longitude, latitude, degrees, learning to be careful when hiking, taking survival food, etc., are all excellent skills. We had a great experience in posting about our geocoin travels and had some unique coins travel to us, including an awesome one from an explosives expert who sent it specifically to my son who was interested in all things military. If you get involved on the Geocaching forum and make friends on behalf of your kids, it can really bring a lot of great new experiences to your homeschooling.